1. Field of the Invention
This invention relates to an ejecting method for ejecting a molding in an injection molding apparatus and a molding produced by using the ejecting method, which is suitable for a precision molding, for example, a spectacle lens.
2. Description of the Related Art
An injection molding apparatus for molding a spectacle lens is mentioned in Japanese Patent Application Publication No. Hei 5-30608.
A molding die used in the apparatus is composed of, as shown in FIG. 7, a stationary die 102 as a lower die and a movable die 101 as a upper die which are separated into lower and upper dies at a parting line PL. The movable die 101, moving to open from and close to the stationary die 102, includes, in turn, a die fitting member 104 and a die body 103 attached to the die fitting member 104 to move toward the stationary die 102. Further, in the die body 103, an insert 120 forming a cavity 122 by being movably put into an insert guide 105 is provided, in which a holding member 129, composed of a back insert holding the insert 120 and the like, is constantly supplied with elastic urging force of an elastic member (not shown) in an opposite direction to the stationary die 102, so that the holding member 129 is abutted to the die fitting member 104 of the movable die 101.
After molten resin is fed into the cavity 122 while the die body 103 of the movable die 101 closes to the stationary die 102, the die fitting member 104, locating a distance from the die body 103 (locating to make an opening from the die body 103 at the degree of slightly opening S), proceeds toward the stationary die 102 with a clamping cylinder (not shown), thereby the molten resin going to be cooling and caking in the cavity 122 is formed to be a specified configuration while being compressed by the insert 120. And further, the die fitting member 104 recedes from the stationary die 102 with the clamping cylinder (to make an opening at the degree of slightly opening S), and at the same time, the movable die 101 is opened from the stationary die 102. The holding member 129 is moved to be pushed toward the stationary die 102 when shifting an eject-pin 120 toward the die fitting member 104, so as to move the insert 120, thereby the molding in the cavity 122 of the movable die 101 is pushed out with the insert 120.
In the conventional art as described thus far, when the die fitting member 104 recedes with the clamping cylinder, the holding member 129 holding the insert 120 is constantly abutted in the opposite direction to the stationary die 102 to be in contact with the die fitting member 104 by being supplied with elastic urging force of the elastic member, so that the insert 120 recedes from the die body 103 together with the die fitting member 104. Resulting from the retreat, a space equal to the degree of the retreat (the degree of slightly opening S) is formed between the molding in the cavity 122 and the insert 120. Therefore, as shown in FIG. 8, when the molding is pushed out from the cavity 122 with the insert 120 by moving the holding 129 to push toward the stationary die 102 by the eject-pin 134, air between the molding and the insert 120 is, firstly, compressed, and then by the compressed air, the molding is pushed out from the cavity 122.
That is to say, the molding is not directly pushed out with the insert 120, and is pushed out by the compressed air like an air gun. Regarding this point, the compressed air damages the molding, resulting in possibility that a molding precision of the molding is reduced.
Especially, in the case the above molding is a spectacle lens, the surface of the lens is harmfully influenced by compressed force caused by the compressed air, resulting in possibility that the high-precise lens cannot be ensured.
It is an object of the present invention to provide the ejecting method of the molding in the injection molding apparatus and the molding produced by using the ejecting method, in which the molding can be pushed out with control of producing the compressed air and the high-precise lens can be ensured.